The use of high resistance materials in the preparation of antifuse structures have been extensively studied in recent years. These studies have indicated that the addition of compounds such as silicon dioxide, silicon nitride or dielectric materials, i.e. nitride/oxide dielectric, polysilicon, to the preparation of antifuse structures resulted in a successful development in application to FPGA's (see Y. Shacham-Diamand, IEEE Trans. Electron Devices, 1993, vol. 40, p. 1780) These antifuses offer significant improvement, such as on-resistance, programmed voltage or other characteristics compared with other programmable elements (A. E. Gamal et.al. reported in IEEE J. Solid-State Circuits, 1989, vol. 2 4, p. 3 94).
Despite the success of such antifuse structures, however, some problems still remained. These problems include: 1) high temperature in dielectric preparations resulting in steam oxidation; 2) on-resistance levels that are not low enough (&gt;50.OMEGA.); 3) insufficiently gathered distribution; and 4) unadjustable forward reverse voltages.
These problems have effectively limited the use of dielectric-based antifuse structures to very large integrations of FGPA. In addition, current indications are that the metal used in MIM structures based on nitride/oxide/nitride insulators are incompatible with VLSI processes.